Solids and soft solids are widely used forms of antiperspirant products. Such products commonly comprise antiperspirant active, carrier oil and structurant. The majority of these solid and soft solid products are anhydrous suspensions, a large portion of which employ fatty alcohol, e.g., stearyl alcohol, optionally in combination with one or more additional structurants. In such products, the antiperspirant active commonly comprises astringent aluminum salt, typically astringent aluminum/zirconium salt, suspended in a matrix formed by a combination of carrier oil and structurant.
The literature suggests numerous volatile and non-volatile oils for use in antiperspirant suspension compositions. To impart desirable sensory properties a large portion, frequently upwards of 40% of the carrier oil, is comprised of volatile oil. Volatile oil tends to impart a dean, dry fed to the applied composition, as well as to contribute to smooth product application and glide. Additionally, volatile oil aids in fragrance delivery.
Within the industry, the volatile oil of choice is commonly volatile silicone oil, e.g., cyclomethicone. Cyclomethicone is nominally designated as D4, D5 or D6, depending upon the particular cyclomethicone (e.g., cyclotetrasiloxane, cyclopentasiloxane or cyclohexasiloxane) predominant therein. The widespread use of cyclomethicone in anhydrous antiperspirant suspensions stems, in part, from its solubility and/or compatibility with numerous carrier oils and structurant ingredients, as well as on the ability of the material to contribute a clean, dry, silky fed to the compositions in which it is employed. While cyclomethicone has sufficient volatility to impart desirable sensory attributes, compared to many other volatile oils, a significant amount of the cyclomethicone tends to be retained in the suspension composition, as opposed to being lost to evaporation. Volatile retention plays an important role in a product delivering equivalent sensory performance over its useful pack life and is also a factor in product stability. Additionally, the surface tension and spreadability of cyclomethicone contributes to products having a smooth or silky feel on application.
When the processing temperature required by the structurant exceeds the flash point of one or more oil components (which is frequently the case when volatile oil is present) processing and material handling considerations may complicate production. Minimizing volatile oil may offer producers certain manufacturing advantages, and may also be desirable from an environmental or regulatory perspective.
In addition to antiperspirant suspension compositions, cyclomethicone is the volatile oil of choice in many other cosmetic products, including products for skin and hair. Cyclomethicone generally, and D5 in particular, is much in demand across a large segment of the cosmetics industry. Recently, the widespread use of cyclomethicone has given rise to issues regarding material availability and sourcing.
While reducing volatile oil content may be desirable conceptually, the concept represents presents considerable formulation difficulties given both the relatively high level at which volatile oil is typically present in antiperspirant suspension compositions and the functions that it performs (which functions are, to a large extent, linked to the material's volatility). Significantly reducing the volatile content of such antiperspirant compositions represents a fundamental change to industry practice. Not only must the replacement material meet the health and environmental requirements for cosmetic products, it should also satisfy the processing requirements of the products into which it is incorporated. Additionally, the replacement material should not degrade a product's physical properties to an unacceptable extent. Desirably, the replacement material should provide a composition that, in use, delivers acceptable sensory and aesthetic properties (e.g., low whiteness, smooth texture and acceptable fragrance to name a few).
Removing volatile oil can result in antiperspirant compositions that are perceived as being greasy, oily, and/or sticky, and/or as taking a relatively long time to dry. Additionally, reformulation to remove volatile oil can significantly affect the physical properties of the composition itself, e.g. payout, hardness, integrity, uniformity, and the like, as well as the texture, whiteness, and appearance of the deposited product. The materials that replace the volatile oil can also give rise to different sensory characteristics depending not only on the properties of the replacement materials themselves, but also on the particular base compositions into which the replacement materials are incorporated. That is to say, performance of a replacement material can be impacted by structurant and oils with which the replacement material is employed.
Reformulation is also impacted by the relatively high level of antiperspirant active present in antiperspirant compositions, typically 10 weight percent or more. Moreover, the antiperspirant active particles are generally of such a size and weight that relatively rapid cooling is required to limit settlement thereof during cooling. Particle sedimentation can give rise to a non-uniform distribution of active in the solidified product; in turn, this can give rise to differences in the delivery of active over the useful pack life. Sedimentation can be exacerbated when the difference between the melt or processing temperature and the solidification temperature is relatively high.
To inhibit sedimentation, antiperspirant suspension compositions, and suspension sticks in particular, tend to be cooled relatively rapidly. By way of comparison, cosmetic suspensions that lack a suspended solid prone to settlement, e.g., lipsticks, may be cooled more slowly. Rapid cooling, while useful in limiting settlement, can give rise to issues with respect to solidification/crystallization of the structurant and the quality of the resulting product. Removing a substantial portion of volatile oil in an antiperspirant suspension composition can impact solidification, crystallization and/or sedimentation behavior.
The presence of antiperspirant active can pose addition complications from a sensory perspective. Even in compositions having volatile oil to contribute to desirable sensory properties, the size and relatively high content of suspended antiperspirant particles may present challenges as regards overcoming active associated drag, particularly in solid sticks. Overcoming drag can be more difficult when the volatile oil content of a composition is reduced.
There remains a need for an antiperspirant composition in the form of a solid or soft solid suspension composition that provides desirable sensory properties when applied to the underarm, in which composition volatile silicone oil and, more desirably volatile oil (exclusive of perfume oil) in general, is reduced or eliminated.
Accordingly, it is an object of the present invention to provide an antiperspirant composition that overcomes or ameliorate one or more of the issues disclosed above.